Blading assembly



Oct. 14, 1958 L. R. SMITH 2,856,118

BLADING ASSEMBLY Filed July 24,- 1952 `Attorneys United States atent G "a BLADING ASSEMBLY Leslie R. Smith, Indianapolis, Ind., assigner to General Motors Corporation, Detroit, Mich., a corporation of Delaware Application July 24, 1952, Serial No. 300,576

1 Claim. (Cl. 230-133) This invention relates to blading assemblies for elastic fluid dynamic machines such as axial llow compressors and the like, and, more particularly, to an improved blading or vane assembly which facilitates and ensures precise angular positioning of the blades or vanes therein.

The present invention is shown as embodied in a stator ring structure of a type employed in axial flow compressors for gas turbine aircraft engines. Such compressors generally comprise a cylindrical stator casing which supports a number of axially spaced rows of stationary vanes and encloses a rotor which mounts a plurality of rows of rotor blades that cooperate with th-e stator vanes to form successive axial stages of the compressor. Each row of stator vanes is mounted in a ring structure which comprises a pair of spaced support members in the form of substantially at outer and inner arcuate strips between which is mounted a number of radially spaced blades or vanes each of which has a tenon or tang formed at the ends thereof. The tenons are received in apertures formed in the arcuate strips and are secured to the respective strips, as by heading or bonding, to constitute a rigid assembly.

The stator vanes of the compressor guide the air or gas from the outlet of each rotating stage Ito the inlet Y of the succeeding rotating stage. In order to obtain the optimum operating characteristics from the compressor, it is essential that the stator vanes be accurately aligned or oriented in the ring structure.

Accurate alignment of the blades or vanes can be obtained by providing closely fitting apertures in the arcuate supporting members so that the blade tenons will be in continuous engagement or contact with the walls of the apertures. This expedient, however, renders the assembly of such structures diicult as the tenons cannot be inserted easily in closely fitting apertures and increases manufacturing costs due to the added handling required thereby. Moreover, slight deviations in the dimensions of the tenons or the openings in the strips may necessitate springing or stressing of the parts in order to force the tenons into the closely fitting apertures. Although the dimensions of the apertures may be enlarged somewhat to obviate the above difficulties, resort to enlarged apertures results in loosely fitting vanes and consequent inaccurate positioning thereof.

Accordingly, the present invention has for its general objects to effect improvements in the construction and quality and reduction of costs of manufacturing blade or vane assemblies of the above described character and, more specifically, to provide an improved form of blade or vane assembly which greatly expedites and facilitates the ease of installation and yet affords precise angular positioning of the blades or vanes therein.

The nature of the present invention and other objects, features and advantages thereof will appear more fully from the following detailed description and drawings, wherein:

Fig. l is a transverse view of a portion of a stator vane assembly which embodies the present invention;

Patented Oct. 14, 1958 Fig. 2 is an enlarged longitudinal sectional view taken in the plane 2 2 of Fig. 1;

Fig. 3 is a plan view taken in the plane 3 3 of Fig. 2; and

Fig 4 is a fragmentary elevation view illustrating the appearance of an upset stator vane tenon as may be employed in the assembly of Fig. 1.

Fig. 5 is an enlarged diagrammatic view of a vane tenon positioned in a receiving aperture conforming to that employed in a vane assembly in accordance with the invention.

Referring to the drawings, Fig. l is a transverse view of a portion of a stator vane assembly of one of the stator stages of an axial flow compressor or turbine used in gas turbine aircraft engines and comprises a pair of concentric spaced arcuate strips or shroud bands 10, 12 between which is mounted a number of radially extending stator vanes 14. The shroud bands 10 and 12 may be semi-circular or of other arcuate extent and are preferably constructed wholly of thin flexible rolled stock, thus resulting in a ring structure which possesses little weight and sufficient structural rigidity.

As best shown in Fig. 2, the outer shroud band 10 comprises a web portion 16 with offset flanges 18, 20 which are adapted to be inserted in one of a number of axially spaced grooves extending circumferentially about the interior of the compressor casing (not shown). The inner shroud band 12 may be of double channel crosssection with superimposed webs 26, 28 and inwardly extending spaced flanges 30, 32, 34 and 36 which form an effective labyrinth seal to prevent the leakage of fluid past the inner tips of the stator vanes.

The stator vanes 14 may be constructed from sheet metal strip stock rolled to an appropriate air foil section as shown in dashed outline in Figs. 3 and 5 with a convex face 40, a concave face 42, a leading edge 44 and a trailing edge 46. The strip stock is cut into sections of desired length, and tenons 48 and 50 are formed at the outboard and inboard ends, respectively, of the airfoil body portion of each blade or vane.. The tenons 48 and 50 may be of unequal axial width. Each tenon has a pair of spaced ends 52 and 54 and arcuate sides or faces 56 and 58, .the latter corresponding to the convex face 41) and concave face 42, respectively, of the airfoil body portion of the vane. The tenons are formed by making a pair of spaced transverse cuts and generally axially directed cuts in the ends and edges of the vanes and removing the material between intersecting transverse and axial cuts to leave perpendicular shoulders 60, 60 and oblique shoulders 62, 62 adjoining the tenons 48 and 50, respectively, at the opposite ends of the vanes. The axial width l of each tenen measured between the spaced ends 52 and 54 thereof is less than the axial width or chord length L of the vane which is measured along a straight line extending between the leading and trailing edges 44 and 46 of the vane'.

The body portion of the vane, which extends between the shoulders at the opposite ends of the vane, is tapered slightly as shown in Fig. 2 and may be twisted from the inboard to the outboard end thereof.

The tenons are received in elongated slots or apertures shown at 64 which are punched or otherwise formed in the web portions of the outer and inner shroud bands 10 and 12. The openings formed in the webs of the inner shroud band 12 are similar to the openings in the outer shroud band 10 but may be of greater length to conform to the greater axial length of the inboard tenon 50 and may be oriented at a dierent angle to the axis of the ring structure than the openings in the outer shroud band in accordance with the angle of twist of the blade. It will be appreciated that the fact that the blades or vanes may be twisted renders insertion and proper alignment of the vanes in the ring structure still more dicult.

As best shown in Fig. 5, each of the apertures 64 comprises-tat-tpairr of spaced-side-zwalls 66, 68 and end walls 70, 72 joining the side walls; 66 isiof" arcuate or concave form' and the opposite side wall 68 may be flat or straight. opening 64-measured between the end walls 70 and"72 is made substantially equal to or slightlyy `greater than` the axial length l of the tenon to be received therein. The concave side wall 66 of the aperture is slightlyv less curvedithantthe adjacent convexside-orface 56 of the tenonby making the radius of curvature R1 of the side wall 66 slightly greater than the average radius of the/convexsideorface of the tenon. The convex side "6 ofthe tenonA will thus abut or Contact theconcaveside wall 66 of the opening 78- at a point intermediate the ends oft-the tenon. The` width W of the elongated slot or opening measured from the point of contact or tangency 78 normalto theside wall 68 is greater than the thickness of the tenon and is` made at most equal to and could be slightly less than the distance from the point 78k normal to a straight linev extending between the extremities of the concave side or face .'53 of the tenori.

The edges 74 and 76 formed between the extremities of the forward or concave faceSS and the ends 52 of the tenon will thus be in rm engagement or contact with the straight side wall 6 of the openingalon'g these'two pointsV and the vane will be properly oriented or posi tioned by reason thereof. Since the width of Ithe opening is such that point Contact 78 is made between the back or convex face 56 and the concave side wall 66 of the opening, the tenori will be maintained securely in the opening and thevane will have no angular motion when installed in the ring` Since the central portion of the concave side or face 58 of the tenen and the portionson the opposite sides of the point 7S on the convex side or face 56 of the tenen are relieved from the corresponding side walls of the openings, the installation of the tenons in the openings is greatly facilitated and expedited. The invention thus provides the advantages ofv an enlarged opening from the standpoint of facilitating insertion of the vane tenons therein as well asthe advantages of a closely fitting opening from the standpoint of ensuring accurate and secure positioning of the tenons therein. The clearance between the walls of the openings and faces of the tenons has been exaggerated slightly in the drawings for the purposek of illustrating `the invention more clearly. Lesser spacings may be employed, if desired.

In assembly, the vanes are mounted with the tenons projecting through .the shroud bands 10, 12 so that the shoulders 6i), tand 62, 62 adjoining the tenons bear firmly against the inner and outer surfaces, respectively, of the outer and inner bands and are held temporarily in assembled relationship. After positioning of the vanes between the shroud bands, the tenons at the opposite ends of each of the vanes are then suitably secured thereto. The stator vanes in the earlier stages of the One of the sidel wallsl The length of the-v CIT compressor may be effectively secured to the shroud bands by brazing the tenons thereto with the material of the braze owing into and tilling the spaces between the tenons and the walls of the openings. The tenons of the vanes in the later stages of the compressor may be headed preferably byvhot electrical upsetting, for example, to cause the tenon material to till the opening and flow around the periphery thereof as shown in Fig. 4 so as to prevent movement of the mounted vanes and to constitute a strong, rigid and unitary structure.

Although the invention has been illustrated and described as embodied in a stator ring structure, it will be understood the invention may be employed in the production of other articles as well.

I claim:

In a sheet metal stator blading assembly for a tiuid dynamic machine including a pair of radially spaced concentric shroud bands. adapted to be supported'from a stator casing and providing a permanent annular support structure. for a` plurality of vanes operativelymounted therebetween, said vanes extendingradially between said shroud bands and having reduced ends f'orm-- ing tenons, each tenon having curved side facesv and straight end faces, said curved side faces includinga convexA face and an opposite concave face, each ofv said shroud bands having a plurality of similar elongated` Walled openings therein for receiving the tenons of said vanes, each of said openings being defined by spaced side walls and end walls joining the side walls and corresponding approximatelyto the shape of said tenons,- the net etfective cross-sectionalarea of each of said open` ings exclusiveof manufacturing tolerances being slightly greater than the cross-sectional area of a tenon received therein, the curved side faces of said tenons' being in operative engagement with the side walls of respective ones of said openings atonly three widely spaced points two of which points lying at the in triangular relation, corners formed by the ends of the concave face with .the straight end faces of the tenon contacting one of the side walls of each of said openings at the ends thereof, and the third of said points lying on the convex face of the tenen contacting the other of the side walls of each of said openings intermediate the ends thereof, whereby said vanes may be inserted readily between said shroudbands and be accurately positioned prior to permanent attachment of the tenons thereof to said shroud bands.

References Cited in the file of this patent UNiTED STATES PATENTS 

